In U.S. Pat. Nos. 3,362,956 and 3,472,854 there are described a number of 1-(heterocyclylalkyl)piperazines having depressant activities on the autonomous nervous system, the cardiovascular system and the skeletal muscular system. The compounds of this invention differ from such known compounds essentially by the nature of the benzimidazole group or the position where the piperazinylmethyl moiety is substituted thereon.